1. Field of the Invention
This invention relates to a combination needle cannula and cannula lock which is to be interfaced with a prefilled medication carpule at the interior of a hypodermic syringe so that the cannula can either be locked at an axially extended position for administering an injection or released from the axially extended position and retracted within and completely surrounded by said carpule, whereby the cannula may be safely discarded after use while avoiding an accidental needle stick and the possible spread of disease.
2. Prior Art
In U.S. Pat. No. 4,808,169 issued Feb. 28, 1989, which has been assigned to the assignee of the present invention, safety syringes are disclosed which have a prefilled medication carpule, a double ended hypodermic needle cannula, and means by which the needle cannula may be relocated from an axially extended position, at which the contents of the medication carpule are injected into a targeted tissue area, to a retracted position, at which the cannula is retracted within and completely surrounded by the carpule. Moreover, a pair of movable jaws was also disclosed for either retaining the cannula in the axially extended position or releasing the cannula for retraction into the carpule.
The present invention is directed to another embodiment of a safety syringe and, more particularly, to an efficient and reliable locking means by which a double ended needle cannula may be either retained in an axially extended position for administering an injection or released from the axially extended position to be retracted within and surrounded by an empty medication carpule. However, rather than the generally one-piece locking arrangements which are characteristic of the safety syringes of the above-mentioned co-pending patent application, the presently disclosed locking means is characterized by multiple components having particular dimensions, whereby to facilitate the manufacture and handling (i.e. during packaging) of the syringe and permit the cannula and locking means to be received by a conventional syringe cylinder without making modifications thereto. Nothing is known which is the same as or equivalent to the presently disclosed combination needle cannula and needle cannula locking means by which the position of a cannula relative to a medication carpule may be selectively and reliably controlled.